1. Field of the Invention
The invention relates to an improved process for the catalytic ammoxidation of paraffins containing from 3 to 5 carbon atoms to .alpha.,.beta.-unsaturated mono-nitriles, especially paraffins containing 3 to 4 carbon atoms. In particular, the present invention is directed to the ammoxidation of isobutane to methacrylonitrile and especially of propane to acrylonitrile.
Because of the price differential between propylene and propane, an economic incentive exists for the development of a viable catalytic process for conversion of propane to acrylonitrile.
Previous attempts to develop an efficient process for the ammoxidation of propane to acrylonitrile produced either insufficient yields of acrylonitrile or processes wherein the catalyst used for the reaction did not have sufficient lifetime characteristics to make the process economical. For example, U.S. Pat. Nos. 4,000,178, 3,833,638, 4,010,188 and 3,746,737 are related to the ammoxidation of propane to acrylonitrile using various types of catalyst systems wherein an halogen promoter is used during the reaction. In addition, Great Britain Patent 1,333,639 relates to ammoxidation of propane using a bismuthmolybdenum catalyst system and a halogen promoter. In each of these cases, either the catalyst utilized does not have a sufficient lifetime characteristic to make the process economically viable or the yields of acrylonitrile obtained during the process are unattractive from a commercial standpoint.
More recently, U.S. Pat. Nos. 4,767,739; 4,784,979; 4,879,264; 5,094,989; 4,837,233; and 4,877,764 are directed to propane ammoxidation to acrylonitrile utilizing mixed metal oxide catalyst and novel procedures for processes for preparing these catalyst which produce improved yield. However, these systems can be improved and the present invention is directed to such an improvement.